This invention relates to a process for the encapsulation or encasement of a sensitive component in a protective housing made of a synthetic resin, with a force-locking fixation of the component within the protective housing and to the assembly protective body and the sensitive component.
Electrochemical and electronic structural elements must be installed in devices exposed to extreme mechanical stresses (vibration, shock) during shipping, storage, or operation in such a way that the aforementioned stresses do not result in damage to these structural elements with ensuing uselessness of the primary device. This holds true to a special extent for ammunition. A process, presently finding general acceptance, for avoiding vibration- or shock-induced damages to the structural elements makes use of the properties of certain curable synthetic resins which are fluid prior to a curing step (during the "pot life") and, after curing, exhibit the desired mechanical properties (high strength and toughness, and high shock-absorbing capacity by plastic deformability).
This arrangement is based on the premise that the components to be installed must be cast together with the structure of the device to form a unitary, solid body to attain the desired properties.
The required mechanical characteristics are usually obtained by synthetic resin systems, e.g., multi-component epoxy resins, in part with the addition of shock-absorbing extenders, such as, for example, hollow glass microspheres. The required mixture ratio of the reactive ingredients must be maintained within narrow limits to avoid the possibility of incompletely reacted mixtures; such mixtures, on the one hand, do not attain the desired values of the mechanical properties and, on the other hand, are capable of releasing chemical compounds deleterious to the other substances and materials present, and also, in case of ammunition, to explosive compounds. A considerable array of expensive tests must be carried out to ensure the correct mixture ratio. The operating units for the processing and metering of the reactive components are technically expensive and require intensive servicing.
The aforementioned synthetic resin systems reach the desired values for their properties only during the course of the curing reaction which takes typically several hours at an elevated temperature. For this reason, temperature-controlled chambers are required for the processing of such synthetic resin systems, wherein the case or molded appliances must be stored during the curing reaction. This necessity increases technical expenditure and represents a stage where manufacturing capacity is reduced.
The reactive components of the synthetic resin systems must be considered to be dangerous working materials, the use of which places considerable demands on the monitoring of the respective working places with regard to working hygiene and safety procedures.
In the process of protecting components against shock- or vibration-induced damage with the use of potting materials according to the state of the art, the necessary electrical connections (wires, stranded conductors, flexible printed wiring conductors) are, in the normal case, likewise enclosed flush with molded appliance. If the cured element is, for example, subjected to stress by a shock, surpassing the prevailing cohesion forces, then the potting material will be torn open and, as experience has shown, the same will happen to the encompassed electrical connections--especially flexible printed wiring conductors. In this way, losses of function can arise even though there is no damage to the active and passive electronic components to be protected.